I just purchased Galder, a smart, difficult puzzle board game from Fast Forward Software. The graphics are lush and realistic and the music is unique; after playing for 15 minutes, I was hooked.
The game can be purchased for Mac OR universal (i.e. Windows, 'nix..whatever). You can download a demo copy at the developer's site: http://www.fastforwardsw.com/
I'm guessing it would be a hit on Game Giveaway.
I'll give you a hint...ALL of the rings move to align (or misalign) the playing pieces.